Growth and mortality of the narrowbarred Spanish Mackerel, Scomberomorus commerson (Lacepède), in Omani waters

Abstract

Length composition data from quarterly catches of Omani narrowband Spanish mackerel, Scomberomorus commerson (Lacepède), landed between 1987 and 1995 were used to estimate the growth, mortality and exploitation parameters of the stock. Non‐linear least square fitting provided a complete set of von Bertalanffy growth estimates: L∞ = 173.6 cm fork length; K = 0.28; and t0 = −0.86 years. There were no seasonal differences among the growth estimates. The instantaneous natural mortalities determined by three independent methods based on life‐history parameters were 0.35, 0.64 and 0.77. Seasonal total mortalities were calculated by the length converted catch curve method for evaluating seasonal exploitation ratios (E). The E‐values exceeded 0.4, indicating overexploitation during almost all the seasons studied. This was supported by the large reduction in the total landings of S. commerson from 27 762 t in 1988 to 3265 t in 1993.